The invention relates to torque transmitting systems in general, and more particularly to improvements in friction clutches of the type normally employed in the power trains of motor vehicles, for example, to transmit torque between the rotary output element (such as a camshaft or a crankshaft) of a prime mover (such as an internal combustion engine) and the rotary input element of a manually shiftable, automated or automatic change-speed transmission. Still more particularly, the invention relates to improvements in friction clutches of the type embodying a unit or assembly which compensates for wear upon certain constituents (particularly the friction linings of the clutch plate or clutch disc), namely for wear which is attributable to or is a consequence of repeated engagement and disengagement of the clutch during extended periods of time, particularly during the entire useful life of the clutch.
Friction clutches of the above outlined character are disclosed, for example, in published German patent applications Ser. Nos. 42 39 291 (corresponding to U.S. Pat. No. 5,450,934 granted Aug. 19, 1995), 43 06 505 (corresponding to U.S. Pat. No. 5,634,541 granted Jun. 03, 1997), 42 39 289 (corresponding to U.S. Pat. No. 5,450,934 granted Sep. 19, 1995), 43 22 677 (corresponding to U.S. patent application Ser. No. 08/211,020 filed Jan. 6, 1995), 44 18 026 (corresponding to U.S. patent application Ser. No. 08/250,760 filed May 28, 1994), 44 31 642 (corresponding to U.S. Pat. No. 5,588,517 granted Sep. 13, 1994) and 195 10 905 (corresponding to U.S. Pat. No. 5,632,365 granted May 27, 1997). The disclosures of all patents and patent applications which are identified in the specification of the present application are incorporated herein by reference.
As a rule, a friction clutch of the character under consideration in the specification and in the claims of the present application comprises a rotary housing or cover, a pressure plate which is rotatable with and has limited freedom of axial movement relative to the housing, and at least one clutch spring (normally a diaphragm spring and hereinafter referred to as diaphragm spring) which serves to urge the pressure plate axially and away from the housing for the purpose of engaging the friction clutch. The purpose of the aforementioned compensating unit is to compensate for wear at least upon the friction linings which form part of the clutch disc and are clamped between the pressure plate and an engine-driven counterpressure plate (such as a flywheel) when the clutch is at least partially engaged. More specifically, the compensating unit ensures that the bias of the diaphragm spring upon the pressure plate in the engaged condition of the friction clutch remains at least substantially constant during the useful life of the clutch (i.e., regardless of the extent of wear upon the friction linings and preferably upon the friction surfaces of the pressure plate and counterpressure plate, as well as upon certain additional constituents (such as various springs) which are subject to wear in response to repeated engagement and disengagement during the useful life of the friction clutch)